Temporary tattoos fitted with electronics make flexible, ultrathin sensors.

Modern methods of measuring the body’s activty, such as electroencephalography (EEG), electrocardiography (ECG), and electromyography (EMG), use electrical signals to measure changes in brain, heart, and muscle activity, respectively. Unfortunately, they rely on bulky and uncomfortable electrodes that are mounted using adhesive tape and conductive gel—or even needles. Because of this, these types of measurements are limited to research and hospital settings and typically used over short periods of time because the contacts can irritate skin.

These limitations may be at an end, however. New research published in Science describes technology that allows electrical measurements (and other measurements, such as temperature and strain) using ultra-thin polymers with embedded circuit elements. These devices connect to skin without adhesives, are practically unnoticeable, and can even be attached via temporary tattoo.